Flexible electronics, also known as flex circuits, is a technology for assembling electronic circuits by mounting electronic devices on flexible web substrates, such as polyimide, PEEK or transparent conductive polyester film. Additionally, flex circuits can be screen printed silver circuits on polyester sheets or other similarly flexible sheets. With lower manufacturing costs than traditional silicon-based devices, and the ability to flex, this technology enables many computing and display applications. For example, this technology can also be used to produce photovoltaic cells and LED lighting panels. This processing method is known as roll-to-roll processing, web processing, reel-to-reel processing or R2R processing.
To mass-produce flexible electronics at high volume and low cost, manufacturers are developing roll-to-roll technology to provide inline processing of wide and long rolls—up to 1 meter wide and 2000 meters long. There are manufacturers who can produce these rolls of materials, but the manufacturing process leaves small defects on the surface of the material in the range of 0.5 microns to 250 microns.
Various steps in the device manufacturing process also produce defects on the working surface of the web material. The defects from these roll manufacturing processes and the device manufacturing processes can interfere with device processing and lead to low overall yield of working devices from the roll of flexible electronics.
It is difficult to remove these very small defects from the surface of the flexible electronic web roll. They are tightly bonded by electrostatic forces, in particular, Van der Waals forces, which are too strong to be overcome by ordinary washing techniques such as rinsing. Solvent-based cleaning solutions can damage the devices and cannot be used effectively.
Cleaning the surface of the flexible electronics web with an adhesive roll is possible, but rapid buildup of defects on the adhesive roll will make it ineffective very quickly. Furthermore, most adhesives will be too sticky and either damage the surface or transfer some material to the flexible electronics web roll. Such transfer will also cause yield loss and reduce the number of working devices created on the surface of the flexible electronics roll.
Cleaning systems do exist today for flexible electronics web that make use of a single or double roller. FIG. 5 illustrates an example of a commercially-available cleaning system that uses rollers. The roller (16) is made of an adhesive material, typically silicone. This material is cleaned by a roll of adhesive tape (15), that can be discarded periodically. However, the silicone roller (16) must make repeated contact with the roll 15 to be cleaned. In addition, a small cleaning surface area is repeatedly contacting a long roll of material. The cleaning must be stopped to change the adhesive cleaning roll, so there is a significant trade-off between cleanliness and line stoppage. Once there is a buildup of larger particles on the adhesive tape, it will no longer effectively clean the roller. Also, this technique does not clean small particles well due to the electrostatic bonding of the small particles discussed above.
Therefore, a need exists in the field for novel cleaning material that can remove the defects from the surface of the flexible electronics roll without sticking or transferring material. There is also a need for a device that enables this material to be run continuously as the long flexible electronics roll is running through the manufacturing process. There is also a need for another material that can remove defects/debris from the cleaning material so it can be used multiple times on the very long rolls of material, and there is need for a device to apply the defect-removal sheet to the cleaning sheet.